1. Technical Field
The present invention relates to a method for making a microwavable package having a permeable compartment constructed using a modified vertical form, fill, and seal packaging machine, and the apparatus and method for making same, that provides for a single piece construction of the package. The invention allows for use of existing converter and packaging technology to produce a microwavable package having one or more permeable compartments with minimal increased cost and minimal modification.
2. Description of Related Art
Vertical form, fill, and seal packaging machines are commonly used in the snack food industry for forming, filling, and sealing bags of chips and other like products. One such packaging machine is seen diagrammatically in FIG. 1. This drawing is simplified and does not show the cabinet and support structures that typically surround a machine, but it demonstrates the working of the machine well. Packaging film 110 is taken from a roll 112 of film and passed through tensioners 114 that keep it taut. The film then passes over a former 116, which directs the film into a vertical tube around a product delivery cylinder 118. As the tube is pulled downward by drive belts 120 the vertical tube of film is sealed along its length by a vertical sealer 122, forming a back seal 124. The machine then applies a pair of heat sealing jaws 126 against the tube to form a transverse seal 128. This transverse seal 128 acts as the top seal on the bag 130 below the sealing jaws 126 and the bottom end seal on the bag 132 being filled and formed above the jaws 126. After the transverse seal has been formed, a cut is made across the sealed area to separate the finished bag 130 below the seal 128 from the partially completed bag 132 above the seal. The tube is then pushed downward to draw out another package length. Before the sealing jaws form each transverse seal, the product to be packaged is sent through the product delivery cylinder 118 and is held within the tube above the transverse seal 128. The material that is fed into the form, fill and seal machine is typically a packaging film such as polypropylene, polyester, paper, polyolefin extrusions, adhesive laminates, and other such materials, or from layered combinations of the above. For many food products, where flavor retention is important, a metalized layer will form the inner most layer.
One modification to a vertical form, fill, and seal packaging machine is disclosed in U.S. Pat. No. 6,722,106 (“the '106 Patent”), which is assigned to the same assignee as the present invention. The '106 Patent discloses a method for making a free standing package called a vertical stand up pouch. The modification uses two forming plates 104 and a tension bar 102 to hold the packaging film tube in tension from inside the tube. Tension is applied on the outside of the film and in the opposite direction of the tension provided by the forming plates 104 by a fixed or stationary tucker mechanism 106 positioned between the forming plates 104. When the tucker bar 106 is properly positioned, it provides a crease or fold in the tube of the packaging film between the two forming plates 104. This creates a gusset 135 that permits the package to stand upright on the gusset 135. The crease is formed prior to formation of the transverse seal by the seal jaws 126. Consequently, once the transverse seal is formed, the crease becomes an integral feature of one side of the package.
The vertical form and fill machine thereafter operates basically as previously described in the prior art, with the sealing jaws 126 forming a lower transverse seal (and upper transverse seal for the bag below), and product being introduced through the forming tube 101 into the sealed tube of packaging film which now has a crease on one side. The film is then pulled downward by moving belts 120 and the upper transverse seal is formed, thereby completing the package. An example of the vertical stand up package formed is shown in FIGS. 2a and 2b. The outside layer of packaging film show the graphics 179 oriented 90 degrees clockwise from graphics orientation normally present on a pillow pouch formed by a standard prior art vertical form, fill and seal machine. As shown in FIG. 2b the transverse seals 128 of the vertical stand up package are oriented vertically once the bag stands up on one end as shown in FIG. 2b. FIG. 2a shows the crease 176 that was formed by the tucker bar 106 and forming plates 104 shown in FIG. 1 to create a gusset 135 that permits the package to stand upright. Various modifications of the vertical stand up pouch, methods for making the pouch, and apparatuses for making the pouch are disclosed in U.S. Pat. Nos. 6,729,109 and 6,679,034.
Another self standing flexible pouch is disclosed in U.S. Pat. No. 6,679,630 also assigned to the same assignee as the present invention. FIG. 3a is cross-sectional view of the self standing flexible package disclosed in the '630 Patent. Referring to FIG. 3a, the '630 patent teaches a package 70 having a flap 78 formed by creating a bend 84 in the film to form an inner portion of flap 78. An opening 90 is formed between the inner and outer portions of the flap 78. FIG. 3b shows a completed package 70 in a standing or display position. Referring to FIGS. 3a and 3b, as package 70 is shown standing, flap 78 extends outward and away from back forming pocket 80. To enclose and retain any product within the package a back seal 124 seals the film tube and transverse end seals 128 seal the terminal ends of package 70. The transverse seals 128 also serve to retain the flap 78 to the terminal ends of package 70. Unfortunately, the '630 Patent requires the flap 78 to be manually drawn away from the back for the package 70 to stand erect with the use of a flap 78. Thus, the package requires manual manipulation to stand up. In addition, because packages are typically opened at the transverse seals, product can spill out of the package after the package is opened, when the package is in the stand up position. Thus, there is a need to provide a package having a compartment or pocket that permits the compartment to hold different contents than are held in the main portion of a package when the package stands erect. Consequently, a need exists for a vertical stand-up package having one or more open compartments that are accessible while the package is standing erect that minimizes the use of film. The prior art discloses other containers often associated with TV dinners having multi-compartment food containers where the compartments are adjacent and integrated into the container. Unfortunately, many of these food containers are made from more expensive thermoforming techniques. Consequently, a need exists for a multi-compartment food container that can be made from an economical modification of a vertical form, fill, and seal machine.
Further, a need also exists for an economical method for making a multi-compartment container having a porous wall between the compartments. Such container can be useful for microwave oven applications.